Effects of Inhomogeneity on the Causal Entropic prediction of Lambda

Abstract

The causal entropic principle aims to predict the unexpectedly small value of the cosmological constant Lambda using a weighting by entropy increase on causal diamonds. The original work assumed a purely isotropic and homogeneous cosmology. But even the level of inhomogeneity observed in our universe forces reconsideration of certain arguments about entropy production. In particular, we must consider an ensemble of causal diamonds associated with one cosmology, and we can no longer immediately discard entropy production in the far future of the universe. Depending on our choices for a probability measure and our treatment of black hole evaporation, the prediction for Lambda may be left intact or dramatically altered.

9 pages, 5 figures. V2: appearing in Phys Rev. D, including additional discussion of generic late-time entropy sources and a more general calculation of their effects on the prediction for Λ, along with an updated figure